I. Field of the Invention
The present invention relates to starter drives for an internal combustion engine and, specifically, to a control circuit which applies electrical power to the starter drive in two stages; the first stage being a reduced power level permitting slow engagement of the driving gear of the starter and the driven gear of the engine and the second stage applying full power to the cranking motor cranking the engine at normal speed.
II. Description of the Prior Art
Two stage starter drive systems employing a resistor in a circuit in order to decrease the power of the electric starting motor in a first stage are well known in the art.
West in U.S. Pat. No. 3,584,229 discloses a solenoid having an E shaped core with two windings thereon in order to include a resistor in the series to effect starting of an engine.
A number of systems and improvements thereon have been developed for use with quick-pitch screw-thread type starters. Seilly in U.S. Pat. Nos. 3,124,694; 3,210,554 and 3,399,576 disclose improvements in systems which include a resistance for such a starter. All of these circuits are used in conjunction with a plurality of catch balls which secure a sleeve to the motor shaft when the driving gear is engaged with the driven gear of the engine. These balls prevent inadvertent return of the sleeve to its rest position before the engine is fully started. Similarly, Gubb and Seilly in U.S. Pat. No. 3,358,667 disclose an improved circuit for including a resistance in a quick-pitch screw-thread starting mechanism. Seilly, in U.S. Pat. No. 3,469,106, discloses a similar circuit with a resistance from the motor control circuit. In U.S. Pat. No. 2,727,158, Seilly discloses a further improvement for a quick-pitch screw-thread starter drive mechanism. The improvement therein lies in the use of a catch as shown in FIGS. 1A and 2A of that patent. The novel catch is used to regulate the inclusion or exclusion of a resistance in the control circuit.
Circuits including a resistance to control the motor speed for starting are also known for positive shift starter drive systems. These include Broyden, U.S. Pat. No. 3,433,968, which disclosed a single set of contacts on the plunger of the solenoid which set of contacts act simultaneously with the positive shift arm to the pinion gear. Closing the circuit between these contacts effectively short circuits a parallel resistance circuit, which resistance circuit insures slow engagement of the driving and driven gears. Similarly, Chohan in U.S. Pat. No. 3,866,960 discloses a contact/armature structure and associated circuitry for controlling the power to the cranking motor by means of a parallel resistance circuit which employs a conventional electric relay.